Ferromagnetic Heusler alloys such as NiMnSb may have unique applications to magnetoresistive devices because of their predicted half-metallic band-structure (i.e., 100% spin-polarized at the Fermi level). However, the high temperatures (>500°C) used to date for the synthesis of the ordered alloy in bulk or thin-film form is incompatible with the reliable fabrication of nanoscale multilayer structures from this material. We report on the growth of high-quality polycrystalline thin films, 200–1000Å thick, of Clb-structured NiMnSb by RF-magnetron sputtering of a composite NiMnSb target onto glass and silicon substrates at temperatures as low as 250°C. We have established that substrate temperature, deposition rate and argon gas pressures all play a critical role in obtaining the Clb-structured phase by direct deposition. Optimal conditions result in films whose properties, including lattice parameter, saturation magnetization, resistivity and magneto-optical Kerr rotation spectrum are identical to those of bulk NiMnSb. Additionally, coercive fields as low as a few oersteds make these films compatible with low-field applications.
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